Chronic iliofemoral vein obstruction - an under-recognized cause of exercise limitation.

Local symptoms of chronic venous insufficiency after deep vein thrombosis (DVT) are well described, but little is known about the effect of residual venous obstruction on exercise capacity. We tested our hypothesis that chronic residual iliofemoral vein occlusion (IFVO) after DVT may impair exercise capacity. Nine post-DVT patients with residual IFVO and effort intolerance were studied; a comparison cohort consisted of 11 healthy volunteers. Exercise tolerance was assessed by bimodality incremental symptom-limited cardiopulmonary testing, using leg and arm ergometers. In healthy subjects, leg vein obstruction was modelled by application to the thighs of cuff tourniquets inflated to 30-40mmHg. Leg exercise tolerance as measured by oxygen uptake at peak exercise (peak ?'O-2) was reduced in patients (median 50% predicted (range 36-83%) vs. 88% predicted (67-129%) in normal subjects, p<0.001). Arm exercise tolerance was also reduced in patients, but less severely than in the legs - the median arm: leg ratio of peak ?'O-2 was 0.95 (0.77-1.43) in patients vs. a normal ratio of 0.73 (0.6-1.0) in healthy subjects (p<0.003). In healthy subjects, bilateral leg vein obstruction by tourniquets reduced peak ?'O-2 in leg exercise to 76% predicted (range 55-108%; p<0.001 vs. standard test). In conclusion, the comparison of arm vs. leg exercise capacity in post-DVT patients with residual IFVO and the effect of experimental venous obstruction (thigh tourniquets) in healthy subjects suggest that reduced exercise capacity in patients was at least partially caused by reduced venous return. Chronic venous obstruction should be recognized as a cause of exercise limitation.